What's the Difference Between Biodegradable and Compostable?

I think I can speak for us all when I say: we’re trying our best. We try to be good people: to say “please” and “thank you,” to be kind unto others, to pick up after ourselves when we make a mess, to recycle the things that we can. But our best becomes even better when we’re more informed—which is what brings us to the difference between “biodegradable” and “compostable.” Because without context and information, the labels slapped onto stuff don’t actually mean anything—and, as it turns out, can actually do more harm than good. Let’s get into it, shall we?

Compostable products are those that decompose into natural, nutrient-rich elements, stuff that’s actively good for the environment, within a certain period of time—typically 90 days. However, compostable products are only compostable if they’re in a compostable setting. That means they’re in a special environment with enough nitrogen (food waste, green clippings), carbon (dead leaves and branches), and oxygen to fuel the microorganisms that break all the stuff down. If compostable stuff is put into the trash, it’ll take much longer to decompose, and the resulting sludge won’t have the positive effect on the environment that it would have in a compost pile. But if it’s put in recycling, the effect is even worse: it’ll contaminate the whole batch.

Compostable products are a sub-set of biodegradable products, which are things that bacteria and fungi break down into carbon dioxide, water, and organic material that isn’t harmful to the environment. The problem: pretty much everything is biodegradable at some point, though it can take hundreds of thousands of years for some stuff to break down. (Biodegradable stuff can only be considered “compostable” it breaks down within one compost cycle.) So what makes something “biodegradable,” then? To be labeled as such, it needs to break down within a “reasonable amount of time”: a wishy-washy guideline, for sure. There’s no real legal enforcement for the label, but the loose standard is one year. 

So where does biodegradable stuff…go? The most important answer: NOT IN THE TRASH. In order for biodegradable stuff to break down, it needs oxygen—and you’re not getting a lot of oxygen when you’re buried in a landfill. When biodegradable stuff breaks down without oxygen—or “anaerobically”—it produces methane gas, which is actively harmful to the environment. Some landfills collect the methane gas produced in its bogs to create electricity, but many don’t. So you’re better off recycling the stuff that’s labeled biodegradable, and composting the stuff that’s compostable.

In case you needed any more of a reason to try to follow these guidelines, here’s a little context for how long some stuff takes to break down in a landfill—many of which could be composted or recycled instead:

Apple core: 1 to 2 months or longer
Paper bag: 1 month
Aluminum can: 80-200 years
Plastic milk jug: 500 years
Disposable diapers: 550 years
Glass bottle: 1 to 2 million years
Styrofoam: LITERALLY NEVER, THIS STUFF SHOULD BE ILLEGAL

If you liked this, subscribe to the What's the Difference newsletter here